1. Field of Invention
The present invention relates to tunneling magnetic sensing elements including an insulating barrier layer composed of Mg—O. In particular, the present invention relates to a tunneling magnetic sensing element having an effectively improved rate of change in resistance (ΔR/R) compared with that in the related art, and a method for producing the tunneling magnetic sensing element.
2. Description of the Related Art
Tunneling magnetic sensing elements (tunneling magnetoresistive (TMR) elements) exhibits a change in resistance due to the tunneling effect. When the magnetization direction of a pinned magnetic layer is antiparallel to that of a free magnetic layer, a tunneling current does not flow easily through an insulating barrier layer (tunnel barrier layer) between the pinned magnetic layer and the free magnetic layer; hence, the resistance is maximized. On the other hand, when the magnetization direction of the pinned magnetic layer is parallel to that of the free magnetic layer, the tunneling current flows easily; hence, the resistance is minimized.
A change in electrical resistance due to a change in the magnetization of the free magnetic layer affected by an external magnetic field is detected as a change in voltage on the basis of this principle to detect a leakage field from a recording medium.
Japanese Unexamined Patent Application Publication Nos. 2004-179667, 2002-141583, and 2005-197764 are examples of the related art.
Changing the material of the insulating barrier layer changes characteristics, such as the rate of change in resistance (ΔR/R). Thus, studies have been conducted on insulating barrier layer materials.
For example, in the case of an insulating barrier layer composed of Mg—O, a free magnetic layer has been used, which has a laminated structure with a NiFe sublayer and a CoFe sublayer that is located between the NiFe sublayer and the insulating barrier layer
In the above-described structure, however, a sufficient rate of change in resistance (ΔR/R) has not been obtained. To achieve higher recording density, further improvement in the rate of change in resistance (ΔR/R) has been required.